The present invention is directed to an antenna system and a method that is configured to compute calibration element voltage gain patterns as functions of a digital antenna model and a plurality of complex beamformer voltages, determine calibration through path transfer functions from the plurality of complex voltages, and remove the calibration element voltage gain patterns from the calibration through path transfer functions to determine a beamforming network transfer function. The beamforming network transfer function and the far-field element voltage gain patterns are combined to obtain a system transfer function used to revise a calibration table.
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1. A system comprising: a probe antenna configured to transmit or receive a calibration signal; an antenna including a plurality of antenna elements arranged in an antenna configuration, the plurality of antenna elements providing a plurality of antenna excitation signals in response to the calibration signal; a beamforming network including a beamformer port and a plurality of channels, each channel including a signal conditioning module coupled to a corresponding antenna element of the plurality of antenna elements, the signal conditioning module having a plurality of conditioning states specifying at least one phase state, the plurality of antenna excitation signals corresponding to a plurality of complex voltages at the beamformer port; a control system coupled to the beamforming network, the control system being configured to select a conditioning state of the plurality of conditioning states in accordance with a calibration control rule; a memory configured to store a digital antenna model and far-field element voltage gain patterns corresponding to the antenna configuration, the memory storing a calibration table configured to associate each steering angle in a set of steering angles to beamformer port complex voltages; and a processor configured to compute calibration element voltage gain patterns as functions of the digital antenna model and the plurality of complex voltages, determine calibration through path transfer functions from the plurality of complex voltages, and remove the calibration element voltage gain patterns from the calibration through path transfer functions to determine a beamforming network transfer function, the processor being configured to revise the calibration table based on the beamforming network transfer function.
The antenna calibration system includes a probe antenna that sends/receives calibration signals. An antenna array with multiple elements responds to this signal with excitation signals. A beamforming network with a port and channels connects each antenna element to a signal conditioning module (which adjusts signal phase). These modules have multiple phase states selected by a control system based on calibration rules. A memory stores a digital model of the antenna, far-field voltage gain patterns, and a calibration table (steering angle vs. port voltages). A processor calculates calibration element gain patterns from the antenna model and complex voltages. It determines path transfer functions and then a beamforming network transfer function. The processor uses the latter to update the calibration table.
2. The system of claim 1 , wherein the processor is configured to combine the beamforming network transfer function and the far-field element voltage gain patterns to obtain a system transfer function.
The antenna calibration system, as described in the previous claim, further includes a processor that combines the beamforming network transfer function with the far-field element voltage gain patterns to generate a system transfer function. This function describes the overall performance of the antenna system.
3. The system of claim 2 , wherein the system transfer function associate each steering angle in the far-field element voltage gain patterns to a beamformer port complex voltages in accordance with the beamforming network transfer function.
The antenna calibration system, including the processor combining the beamforming network transfer function with far-field element voltage gain patterns into a system transfer function, now uses this system transfer function to associate each steering angle in the far-field element voltage gain patterns to a corresponding beamformer port complex voltage, in accordance with the beamforming network transfer function. This provides a calibrated mapping between steering angles and the required beamformer port voltages.
4. The system of claim 1 , wherein the set of steering angles is a function of frequency or system temperature.
In the antenna calibration system described in claim 1, the set of steering angles stored in the calibration table is dynamically adjusted based on frequency or system temperature. This allows the system to maintain accurate calibration under varying environmental conditions and operating parameters.
5. The system of claim 1 , wherein the beamformer network includes a receiver circuit, the set of steering angles providing angle-of-arrival information for an electromagnetic signal incident the antenna and received by the receiver.
The antenna calibration system described in claim 1, incorporating a receiver circuit within the beamformer network, uses the set of steering angles to determine the angle-of-arrival information for electromagnetic signals that impinge on the antenna and are received by the receiver. Essentially, it identifies the direction from which a received signal originated.
6. The system of claim 1 , wherein the beamformer network includes a transmitter, the set of steering angles providing scanning information for radiating an electromagnetic signal via the antenna at predetermined angle relative to the antenna's boresight.
In the antenna calibration system from claim 1, if the beamformer network includes a transmitter, the system uses the set of steering angles to control the direction in which the antenna radiates an electromagnetic signal. These angles specify the predetermined direction relative to the antenna's boresight for signal transmission.
7. The system of claim 1 , wherein the antenna configuration is selected from a group of antenna configurations including a non-phased array antenna, a phased array antenna, a planar phased array antenna, a non-planar phased array antenna, a conformal phased array antenna, or a cylindrical phased array antenna.
This invention relates to antenna systems used in wireless communication or radar applications, addressing the need for flexible and adaptable antenna configurations to optimize performance in different environments. The system includes an antenna configuration that can be selected from a variety of options, such as non-phased array antennas, phased array antennas, planar phased array antennas, non-planar phased array antennas, conformal phased array antennas, or cylindrical phased array antennas. Each configuration offers distinct advantages depending on the application. Non-phased array antennas provide simplicity and cost-effectiveness, while phased array antennas enable beam steering and adaptive beamforming for dynamic signal control. Planar phased array antennas are suitable for flat surfaces, whereas non-planar and conformal phased array antennas can adapt to curved or irregular surfaces, improving integration with vehicles, aircraft, or other structures. Cylindrical phased array antennas offer 360-degree coverage, ideal for omnidirectional applications. The selection of the antenna configuration allows the system to be tailored for specific use cases, enhancing signal quality, coverage, and efficiency in wireless communication or radar detection. This adaptability ensures optimal performance across diverse operational scenarios.
8. The system of claim 1 , wherein an antenna element of the plurality of antenna elements is selected from a group of antenna elements including horn antenna elements, reflector antenna elements, dipole antenna elements, loop antenna elements, or slot antenna elements.
The antenna calibration system from claim 1 employs various types of antenna elements within the array, selected from horn antennas, reflector antennas, dipole antennas, loop antennas, or slot antennas. The choice of element depends on the application requirements.
9. The system of claim 1 , wherein the system is configured as a radar system, a sensor system, a communication system, a Multiple Input Multiple Output (MIMO) system or a radiometry system.
The antenna calibration system, as outlined in claim 1, can be implemented in different applications, including a radar system, a sensor system, a communication system, a Multiple Input Multiple Output (MIMO) system, or a radiometry system. This demonstrates the versatility of the calibration method across various fields.
10. The system of claim 9 , wherein the beamformer network further comprises: a beam summer coupled to the a plurality of channels, the beam summer being configured to combine a plurality of incident antenna excitation signals and provide at least one RF sum beam signal; a receiver coupled to the beam summer, the receiver being configured to translate the RF sum beam signal to an intermediate frequency (IF) signal; and at least one digital circuit element configured to convert the IF signal to thus provide at least one received complex voltage at the beamformer port.
When the antenna calibration system from claim 9 (radar, sensor, communication, MIMO, radiometry) is implemented, the beamformer network includes a beam summer combining antenna excitation signals into an RF sum beam signal. A receiver translates this signal to an intermediate frequency (IF) signal, which is then converted by a digital circuit element to produce a received complex voltage at the beamformer port.
11. The system of claim 10 , wherein the control system is configured to select the conditioning state for the plurality of channels in accordance with a predetermined receiver mode control rule.
The antenna calibration system described in claim 10 (radar, sensor, communication, MIMO, radiometry), which uses a beam summer and receiver to get received complex voltage at the beamformer port, further includes a control system configured to select the signal conditioning state for each channel based on a predetermined receiver mode control rule.
12. The system of claim 10 , wherein the control system is configured to retrieve an angle-of-arrival from the set of steering angles in the revised calibration table corresponding to the at least one received complex voltage at the beamformer port.
The antenna calibration system described in claim 10 (radar, sensor, communication, MIMO, radiometry), which uses a beam summer and receiver to get received complex voltage at the beamformer port, utilizes the control system to find an angle-of-arrival from the revised calibration table that corresponds to the received complex voltage at the beamformer port.
13. The system of claim 10 , wherein the control system is configured to retrieve an angle-of-arrival from the set of steering angles in the revised calibration table corresponding to the at least one received complex voltage at the beamformer port.
The antenna calibration system described in claim 10 (radar, sensor, communication, MIMO, radiometry), which uses a beam summer and receiver to get received complex voltage at the beamformer port, utilizes the control system to find an angle-of-arrival from the revised calibration table that corresponds to the received complex voltage at the beamformer port. This repeats claim 12.
14. The system of claim 10 , wherein the control system or the processor is configured to find a monopulse ratio, an angle estimation ratio, a maximum likelihood angle estimation ratio, or a MIMO transfer function corresponding to the at least one received complex voltage.
The antenna calibration system described in claim 10 (radar, sensor, communication, MIMO, radiometry), which uses a beam summer and receiver to get received complex voltage at the beamformer port, employs either the control system or the processor to compute parameters like monopulse ratio, angle estimation ratio, maximum likelihood angle estimation ratio, or MIMO transfer function based on the received complex voltage.
15. The system of claim 10 , wherein the signal conditioning module is a transmit/receive (T/R) module, and the plurality of conditioning states are control bits for receive phase shifters or receive attenuators coupled to the beam summer.
In the antenna calibration system of claim 10 (radar, sensor, communication, MIMO, radiometry), the signal conditioning module is a transmit/receive (T/R) module. The phase states are controlled by control bits for receive phase shifters or receive attenuators coupled to the beam summer. These control the signal characteristics during reception.
16. The system of claim 9 , wherein the beamformer network further comprises: at least one digital circuit element configured to convert a complex voltage at the beamformer port into an analog signal; an upconverter network coupled to the at least one digital circuit element and configured to translate the analog signal into an RF transmit signal; and a beam summer coupled to the upconverter network and configured to split the RF transmit signal into a plurality of RF difference signals.
When used as a radar, sensor, communication, MIMO, or radiometry system, as described in claim 9, the beamforming network includes a digital circuit to convert the complex voltage into an analog signal. An upconverter translates the analog signal into an RF transmit signal. A beam summer then splits the RF transmit signal into multiple RF difference signals for transmission.
17. The system of 16 , wherein the control system is configured to select the conditioning state for the plurality of channels in accordance with a selected transmit steering angle in the set of steering angles.
The antenna calibration system from claim 16 includes a control system that selects the signal conditioning state for each channel based on a selected transmit steering angle from the set of steering angles. This allows the system to direct the transmitted signal in the desired direction.
18. The system of claim 16 , wherein the signal conditioning module is a transmit/receive (T/R) module, and the plurality of conditioning states are control bits for transmit phase shifters or transmit attenuators coupled to the beam divider.
In the antenna calibration system of claim 16, the signal conditioning module is a transmit/receive (T/R) module. The phase states are control bits for transmit phase shifters or transmit attenuators coupled to the beam divider which control the characteristics of the transmitted signals.
19. The system of claim 9 , wherein the processor and the memory are disposed in the radar system housing.
For use in a radar, sensor, communication, MIMO, or radiometry system, the processor and memory are housed within the radar system itself. This makes the calibration components an integral part of the operational system.
20. The system of claim 1 , wherein the processor and at least a portion of the memory are disposed in a calibration system housing.
In the antenna calibration system described in claim 1, the processor and at least part of the memory are located in a separate calibration system housing. This isolates the calibration components from the main antenna system.
21. The system of claim 1 , further comprising a CEM tool configured to generate the digital antenna model and the far-field element voltage gain patterns based on the antenna configuration.
The antenna calibration system from claim 1 can use a computational electromagnetics (CEM) tool to generate the digital antenna model and far-field element voltage gain patterns based on the antenna configuration. This automates the process of creating these critical calibration parameters.
22. The system of claim 1 , wherein the calibration control rule is configured to direct the control system to sequentially operate one signal conditioning module at a time with all other deselected signal conditioning modules being disabled, the control system being directed to sequence through each of the plurality of conditioning states while operating the signal conditioning module.
The calibration control rule directs the control system to activate signal conditioning modules one at a time, disabling the others. For each active module, the control system sequences through each of its available conditioning states. This is a sequential calibration approach.
23. The system of claim 1 , wherein the calibration control rule is configured to direct the control system to operate the signal conditioning modules corresponding to the plurality of channels in accordance with a Hadamard control rule.
The calibration control rule directs the control system to operate the signal conditioning modules according to a Hadamard control rule. This is an alternative calibration strategy potentially offering advantages in terms of speed or accuracy.
24. The system of claim 23 , wherein the Hadamard control rule requires (4+2p)N measurements of the calibration signal, wherein p denotes the number of the plurality of conditioning states.
When using the Hadamard control rule, as described in claim 23, the calibration process requires (4+2p)N measurements of the calibration signal, where p is the number of conditioning states per module and N is the number of antenna elements.
25. The system of claim 1 , wherein the beamforming network transfer function is given by the expression: b(n)=s 0 (n)/ƒ 0 (n), wherein s 0 (n) corresponds to the calibration through path transfer functions and ƒ 0 (n) corresponds to the calibration element voltage gain patterns.
The beamforming network transfer function is calculated as b(n) = s0(n) / f0(n), where s0(n) represents the calibration through-path transfer functions and f0(n) represents the calibration element voltage gain patterns. This equation defines how the beamforming network's performance is determined from the measured and modeled data.
26. The system of claim 25 , wherein the system transfer function is given by the expression: s′(n, θ, φ)=b(n)ƒ(n, θ, φ), wherein ƒ(n,θ,φ) corresponds to the far-field element voltage gain patterns.
The system transfer function is given by the expression s'(n, θ, φ) = b(n) * f(n, θ, φ), where f(n, θ, φ) corresponds to the far-field element voltage gain patterns and b(n) is the beamforming network transfer function. This function describes the overall system performance, combining the beamforming network and antenna characteristics.
27. The system of claim 1 , wherein the antenna excitation signals are generated in response to a calibration signal transmitted by the probe antenna or a calibration signal provided via the beamforming network.
The antenna excitation signals can be generated in response to a calibration signal transmitted by the probe antenna, or alternatively, the calibration signal can be provided through the beamforming network itself. This provides two methods for injecting the calibration signal.
28. The system of claim 1 , wherein the probe antenna is disposed in a near-field of the antenna.
The probe antenna is positioned in the near-field of the antenna array. This allows for a strong and well-defined calibration signal to be injected into the antenna array under test.
29. The system of claim 28 , wherein the probe antenna is coupled to the control system by a communications link configured to establish data synchronization and RF phase lock with the control system.
The probe antenna communicates with the control system via a communications link that ensures data synchronization and RF phase lock between them. This is crucial for accurate calibration.
30. The system of claim 29 , wherein the communication link is selected from a group of communications links that include a wireline communications link, a wireless communications link, a digital communications link or an analog communications link.
The communications link between the probe antenna and control system can be a wireline, wireless, digital, or analog connection. The specific choice depends on system requirements.
31. A method comprising: providing a system comprising an antenna including a plurality of antenna elements arranged in an antenna configuration, the plurality of antenna elements providing a plurality of antenna excitation signals in response to the calibration signal, the system comprising a beamforming network including a beamformer port and a plurality of channels, each channel including a signal conditioning module coupled to a corresponding antenna element of the plurality of antenna elements, the signal conditioning module having a plurality of conditioning states specifying at least one phase state, the plurality of antenna excitation signals corresponding to a plurality of complex voltages at the beamformer port, the system further including a control system coupled to the beamforming network, the control system being configured to select a conditioning state of the plurality of conditioning states in accordance with a calibration control rule, and a memory being configured to store a calibration table configured to associate each steering angle in a set of steering angles to beamformer port complex voltages; storing a digital antenna model and far-field element voltage gain patterns corresponding to the antenna configuration in the memory; propagating a calibration signal; computing calibration element voltage gain patterns as functions of the digital antenna model and the plurality of complex voltages; determining calibration through path transfer functions from the plurality of complex voltages; determining a beamforming network transfer function as a function of the calibration element voltage gain patterns and the calibration through path transfer functions; and revising the calibration table based on the beamforming network transfer function such that a revised calibration table is stored in memory, the revised calibration table being configured to associate each steering angle in a set of steering angles to revised beamformer port complex voltages.
The method begins by providing a system with an antenna array. The array's elements provide excitation signals in response to a calibration signal. A beamforming network with channels and conditioning modules adjusts signal phase. A control system selects the conditioning state based on a calibration rule. A memory stores a calibration table linking steering angles to beamformer port voltages. The method stores a digital antenna model and far-field gain patterns in memory. Then, it propagates a calibration signal, computes element gain patterns from the antenna model and voltages, determines path transfer functions, calculates a beamforming network transfer function based on the previous computations, and revises the calibration table accordingly, thus storing a new association between steering angles and beamformer port voltages.
32. The method of claim 31 , further comprising the step of removing the calibration element voltage gain patterns from the calibration through path transfer functions to obtain the beamforming network transfer function.
The method, as described in the previous antenna calibration method, further includes a step to remove the calibration element voltage gain patterns from the calibration through path transfer functions to get the beamforming network transfer function.
33. The method of claim 31 , further comprising the step of combining the beamforming network transfer function and the far-field element voltage gain patterns to obtain a system transfer function.
The antenna calibration method, as outlined previously, also involves combining the beamforming network transfer function with the far-field element voltage gain patterns to create a system transfer function.
34. The method of claim 33 , wherein the system transfer function associates each steering angle in the far-field element voltage gain patterns to the beamformer port complex voltages in accordance with the beamforming network transfer function.
The antenna calibration method, now creating a system transfer function that combines the beamforming network transfer function with the far-field element voltage gain patterns, utilizes the system transfer function to associate each steering angle in the far-field element voltage gain patterns to the beamformer port complex voltages according to the beamforming network transfer function.
35. The method of claim 31 , further comprising the step of generating the digital antenna model and the far-field element voltage gain patterns based on the antenna configuration prior to the step of storing.
Before storing the digital antenna model and far-field element voltage gain patterns in the calibration method described previously, the method first includes generating the digital antenna model and the far-field element voltage gain patterns based on the antenna configuration.
36. The method of claim 31 , wherein the calibration control rule is configured to direct the control system to sequentially operate one signal conditioning module at a time with all other deselected signal conditioning modules being disabled, the control system being directed to sequence through each of the plurality of conditioning states while operating the signal conditioning module.
In the antenna calibration method described previously, the calibration control rule is designed to have the control system sequentially operate one signal conditioning module at a time, with the rest turned off. When a signal conditioning module is active, the control system cycles through each of its phase states.
37. The method of claim 31 , wherein the calibration control rule is configured to direct the control system to operate the signal conditioning modules corresponding to the plurality of channels in accordance with a Hadamard control rule.
The antenna calibration method can use a calibration control rule that directs the control system to operate the signal conditioning modules based on a Hadamard control rule.
38. The method of claim 37 , wherein the Hadamard control rule requires (4+2p)N measurements of the calibration signal, wherein p denotes the number of the plurality of conditioning states.
When the antenna calibration method utilizes the Hadamard control rule, it requires (4 + 2p)N measurements of the calibration signal. 'p' is the number of phase states for each conditioning module and 'N' is the number of antenna elements.
39. The method of claim 31 , wherein the beamforming network transfer function is given by the expression: b(n)=s 0 (n)/ƒ 0 (n), wherein s 0 (n) corresponds to the calibration through path transfer functions and ƒ 0 (n) corresponds to the calibration element voltage gain patterns.
The antenna calibration method uses an equation for the beamforming network transfer function: b(n) = s0(n) / f0(n). Here, s0(n) is the calibration through path transfer function and f0(n) is the calibration element voltage gain patterns.
40. The method of claim 39 , wherein the system transfer function is given by the expression: s′(n, θ, φ)=b(n)ƒ(n, θ, φ), wherein ƒ(n,θ,φ) corresponds to the far-field element voltage gain patterns.
The antenna calibration method described, which calculates a beamforming network transfer function, also defines the system transfer function as: s'(n, θ, φ) = b(n) * f(n, θ, φ). In this equation, f(n, θ, φ) represents the far-field element voltage gain patterns.
41. The method of claim 31 , wherein the system is configured as a radar system, a sensor system, a communication system or a radiometry system.
The antenna calibration method can be applied to a system used as a radar system, a sensor system, a communication system, or a radiometry system.
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November 19, 2014
October 17, 2017
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